Add zitadel OIDC

[ostempel]

Description

• Remove Dex
• Add Zitadel

PRs:

• skip insecure oidc metal-apiserver#89
• oidc_client_id needs to be a string helm-charts#136
• Add roles for deploying Zitadel metal-roles#493

[ostempel]

Not done yet:

• Roles variables and defaults
• Customize Login page

[ostempel]

Todo:

• add zitadel-db backuprestore variables to release vector

[Gerrit91]

Very keen to try this out. :)